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* V 



The Scientific Aspects of 
Luther Burbank's Work 



By 

DAVID STARR JORDAN 

AND 

VERNON L. KELLOGG 




SAN FRANCISCO 

A. M. ROBERTSON 

1909 



LIBRARY of CONGRESS 
Two Copies Received 

DEC 29 1908 

Copyrignt tntry 
CLASS XXc. No, 

copy's. 



Copyright by 
A. M. ROBERTSON 
1908 



"PMlopoUs "press 
SanTranclsco 



Contents 

Some Experiments of Luther Burbank, 

By David Starr Jordan - - - Page 1 

Scientific Aspects of Luther Burbank' s Work 

By Vernon Lyman Kellogg - Fage 83 



The Illustrations 

Page 

Sample Leaves of Common Garden Dahlia {Dahlia 
variabilis), showing Ordinary Variation within a 
Species when under Cultivation .... 5 

Primus, the First Fixed Rubus Species Artificially Pro- 
duced ........ 10 

Leaves Showing a Number of Strawberry-Raspberry 

Hybrids and a Cluster of the Blossoms . . 13 

Opuntia jicus-indica and its Hybrid with O. vulgaris, the 

Hybrid Flower far Larger than Either Parent . 21 

Diagram Showing the Zone of Life and Parallelism of 

Results in Crossing and Grafting. (L. B. ) . 22 

Stems of Blackberry-Raspberry Hybrids . . . 27 

Leaves of Blackberry Raspberry Hybrids . . . 29 

Leaves of a Blackberry Hybrid, all Grown from Seed of 

One Plant 33 

Apples — all Seedlings from One Variety, ' The Early 
Williams,' showing about the Normal Variation of 
Apple Seedlings . . . . *. . 37 

Seedlings of Japanese Quinces, showing Normal Varia- 
tions ........ 41 

The Original and Improved (Shasta) Daisy . . 43 



V 



The Illustrations 




Page 



Result of Cross of Japan and English Walnut . . 44 
Leaves from Second Generation Seedlings from Cross of 
Common Persian Walnut {Juglans regia) and Cali- 
fornia Native Walnut ... . . . . 45 

Hybrid Mesembryanthemum . . . . . 49 

Sample of Hybrid Poppies . . . . . 51 

Sample Leaves of the Two Species of Bocconia . . 52 
Leaves from Hybrid Poppies . . . . . 53 

Capsules of Second Generation Hybrid Poppies . . 55 
Original Wild Stoneless Plum at the Top, and Fourteen 
of Its Seedlings w^hen Crossed with the French 
Prune Below, about one-fourth Size . , . 57 
The Plumcot — an Absolutely New Fruit ... 61 
Original and Improved Beach Plum .... 61 

Ten Varieties of Plums Grown from the Seed of the 
Burbank Plum Crossed with the Apricot Plum, 
showing Variations ...... 61 

Thallus and Fruit of Spineless Cactus . . . 63 
Bed of Seedlings from Spineless Cactus, showing Here 

and There Reversion to the Original Spinous Form 64 
Edible Cactus or * * Barbary Fig ' ' ( Opuntia ficus-indka) 

from Malta 65 

Thornless Opuntia, with Joints Growing Out from the 

Fruit . 67 



VI 



The Illustrations 




Page 

Two Joints of Opuntia, each with Fifteen Pounds Fruit, 

each Two Years Old ..... 69 
Joint of Opuntia Cut in Two and Planted Bottom Up. 

Fruits of Opuntia, the Larger Planted Bottom Up. 73 
Eleagnus longipes, Japanese Goumberry, Improved by 

Selection ........ 81 

Hybrid Walnut * Paradox ' 93 

One of the Stoneless Plums and Two of its Parents . 95 
Zea Mays (Cuzco Corn), Parent of Indian Corn . 97 
Leaves of Hybrid Blackberry Plants of the Same Par- 
entage ........ 99 

Hybrid Chestnut in Fruit, Six Months Old . . 191 

California Poppy {Eschoschltzia) Rendered Bright Crimson 

as a Result of Selection Only, without Crossing . 103 
Rhodanthe naglesi, a Rose Colored Everlasting Flower 

Improved in Size and Color by Selection Only . 105 
Heuchera Leaves Made Crested by Selection of Varying 

Seedlings ........ 107 



vii 



Luther Burbank 



UTHER BURBANK is a modest, quiet, 
devoted worker in science, with a keen 
eye, a deft hand, a broad intelH^ence and a 
sensitive soul. He has taken up as his 
hfe-work the modification of plant life by 
the processes of crossing and selection. 
He has devoted himself whole-souled to this work, and with 
an industry amazing and almost without parallel. For years he 
has kept thousands of different experiments going, acting on 
the mechanical certainty that in plant-crossing there will be as 
many gains as losses, as many tremendous improvements as 
utter failures. For the sake of the one great gain, he ean burn 
a ton of vegetable debris made up of plants which failed or 
only partly succeeded. 

Mr. Burbank has no patent on his methods. They are as 
open as the day. Thousands have used them before, as thous- 
ands will use them later. But not one in a hundred thousand 
has or will use them with like intelligence, deftness and skill. 

It is Darwin who first gave us the knowledge on which all 
this work rests. The origin of species demands variation, 
selection, segregation, and behind all this the law of heredity, 

ix 




LutherBurbank 




the fact that *Mike produces like" or nearly alike. Burbank 
is a creator of species. So is any man who applies these 
elements to animal or plant life. To call him a ''wizard," as 
some men and some magazines do, is to injure him in reputa- 
tion and to befog his great services with a trivial epithet. 

Burbank' s ways are Nature' s ways, for Burbank differs from 
other men in this, that his whole life is given to the study of 
how Nature does things. His greatest service to science is to 
show what can be achieved through deeper knowledge of things 
as they are. He has shown the infinite variety of Nature as 
exhibited in the varying life and ways of the millions of kinds 
of living things. He has shown the unity of Nature in again 
demonstrating the final essential simplicity of creative processes. 
He has put into practical utility the teachings of his greatest 
master, Darwin, and he has enriched the world with thousands 
of fruits and flowers, useful and delightful, which but for him 
would have existed only among the conceivable possibilities of 
creation. He works in his own way with the tools he needs and 
the methods he can use. He has helped mankind by increasing 
enormously the economic values plant life. He has helped even 
more our science and our philosophy by his practical and success- 
ful test of biologic theories. Among the men of science of cen- 
tury that is, Burbank is assured of a high and honored place, not 
as a ''wizard" or as a clever operator, but as a man of broad 
views, exact knowledge, and noble and ennobling character. 

D. S. J. 

X 



Some Experiments of 
Luther Burbank 

By David Starr Jordan 



David Starr Jordan 




Some Experiments of 
Luther Burbank 

R. LUTHER BURBANK, of 
Santa Rosa, California, is beyond 
question, the most skilful experi- 
menter in the field of the forma- 
tion of new forms of plant life 
by the process of crossing and selection. He 
is the creator of many of our most useful plant 
forms: roots, nuts, fruits, grains and grasses, as 
well as of many of our most beautiful flowers. 
His methods are the practical application of the 
theories of Darwin and his followers, and to a 
degree wholly exceptional among plant breeders, 
Mr. Burbank has kept in touch with most mod- 
ern work in the field of bionomics, and very 
much of his time and energy is devoted to experi- 
ments of scientific interest not likely of them- 
selves to yield immediate practical results. In the 




3 



Some Experiments oj Euther Burbank 




nature of things, the demands of his work, and 
the necessity for the sale of new forms produced 
by him, have prevented the keeping of detailed 
records of his work, although steps have been 
taken toward the provision of explicit records in 
the future. For the rest, Mr. Burbank' s success 
in practical achievement gives weight to his views 
on theoretical questions. 

The process of formation of new types may 
be grouped under four heads: selection, crossing, 
hybridization and mutation (or saltation). The 
process of artificial selection is used in all cases, 
those varying strains likely to prove useful being 
preserved, the others destroyed. The word ' cross- 
ing ' may be advantageously used for the mingling 
of strains within a species, and 'hybridization' 
for the breeding together of members of different 
species. The name * mutation' (or preferably 
* saltation ' ) is applied to sudden changes of char- 
acters for which no immediate cause is apparent. 

Not many of Mr. Burbank' s results are due to 
unassisted selection, as the processes of crossing 

4 




Sample Leaves of Common Garden Dahlia (Dahlia ^variabilis), Showing 
Ordinary Variation nvithin a Species when under Cultivation. 



David Starr Jordan 




and hybridization save time by the increase of the 
rate or degree of variation. There is, however, 
no evident hmit to the results to be obtained by 
simple selection. New and permanent species of 
wheat have, without a shadow of doubt, been pro- 
duced by selection alone. 

In the California poppy (Eschscholtzia califor- 
nica), stripes of crimson are never seen on the 
inside. Mr. Burbank once found a seedling in 
which the outside crimson had struck through like 
a crimson thread which had been misplaced. In 
other generations, by selection, this red was more 
and more increased, until finally out of it is devel- 
oped a crimson poppy, of which Mr. Burbank 
has now many specimens, seeding more or less 
true to the type. The ' Shirley ' poppy (Papaver 
rhceas) is well on the way to blue by selection. 

It is questioned whether competition in minor 
details, or ' intra-specific selection,' can form 
species permanent as wild species are. As to this, 
Mr. Burbank notes that the cultivated species pro- 
duced after the fashion of his crimson eschscholtzia 



7 



Some Experiments by Luther Burbank 




'have a very brief history compared with the 
wild species, and, moreover, they are constantly 
being placed in a new environment by man, 
being influenced by new soils, new climates, 
new fertilizers and the like/ ''Breeding to a 
fixed line will bring fixed results. Man's des- 
ultory breeding is brief, the struggle for exis- 
tence is mostly absent, and new ideals and 
new uses are required instead of ability to 
endure under natural conditions. Man's efforts 
at selective breeding are fluctuating, with frequent 
saltations." 

Dr. De Vries notes that in the common sugar 
beet, which is a biennial species, there are from 
one to ten per cent of plants which bear seed the 
first year. None of these is ever chosen for seed, 
and yet the long-continued process of natural selec- 
tion has never succeeded in rooting them out. As 
to this Mr. Burbank observes: "This long-fixed 
tendency to insure continued existence in the past 
is not yet bred out. Analogous to this is the ten- 
dency in flocks to produce black sheep, and the 

8 



David Starr Jordan 




appearance of zebra stripes on horses — ancestral 
traits not yet bred out." 

From the pale yellow Iceland poppy {Papaver 
nudicaule) are developed white, yellow and orange 
forms, and some with striped petals and a strong 
tendency to become double. Selecting the Ice- 
land poppy for size alone, flowers three and one- 
half inches across have been developed. A large 
scarlet poppy, Papaver glaucum, closes its two 
inner petals when a bee or two have entered, 
shutting in the bees, which buzz angrily and cover 
themselves with pollen until they are set free. If 
not visited by bees, the flowers do not close. 

A wild form of one of the Liliacas, Brodicea 
terrestris, was made white by selection of the palest 
among the pale wild ones. Brodicea lactea taken 
from the high Sierras where it is a dwarf, becomes, 
after two years of cultivation, more than twice as 
high as the original stock, but not nearly as high 
as the same species grown in the valley. 

Crossing is done to secure a wealth of varia- 
tion. By this means we get the species into a state 

9 



Some Experiments of Luther Burbank 




of perturbation or 'wabble/ and take advantage 
of the 'wabbling' to guide the life forces into the 
desired habits or channels. The first crossing is 




Primus^ the First Fixed Rubus Species 
Artificially Produced. 



generally a step in the direction in which we are 
going, but repeated crossing is often necessary and 
judicious selection always necessary to secure val- 
uable practical results. Crossing may give the 

10 



David Starr Jordan 




best or the worst qualities of the parent, or any 
other quahties; and previous crossings often afFect 
the results." 

Hybridization differs from ordinary crossing 
only in degree. A species is only a race which 
has assumed greater fixity. The purposes and 
results of crossing within the species and of hybrid- 
ization of different species are essentially alike. 
The formation of the new individual by the sexual 
relation of two parents is in itself a species of 
crossing, giving each new individual in its degree 
new traits or new combinations." 

' ' Bees and other insects, as well as the wind, 
cross plants, but they do not work intelligently, 
therefore rarely to any advantage economically 
to man. No mechanic could invent such devices 
as those which tend to prevent self-crossing in 
plants. All evolution and improvement are dependent 
on crossing, therefore nature has produced more 
wonderful devices for this purpose than for any 
other." 

"'Mutations, or saltations, are of ten found ; that 



11 



Some Experiments of I^uther Burbank 




is, fixed forms springing up, generally from un- 
known causes, forms which are not hybrids, and 
which remain constant; as, for instance, colored 
flowers which yield white forms, these yielding 
white constantly in their progeny. T^hese mutations 
can he produced at will by any of the various means 
which disturb the habits of the plant. It comes 
out when the conditions are ripe. New conditions 
bring out latent traits. I should expect mutations 
to arise in the American primrose and most other 
plants under wholly new conditions. Extra food 
or growth force as well as crossing favors variation, 
as does abrupt change of conditions of any kind. 
Five or six generations will usually fix a mutation. 
Sometimes it is fixed at once." 

' ' On the average, perhaps about six generations 
fairly fix a variation, but this varies greatly, depend- 
ing upon previously acquired hereditary tenden- 
cies. Bringing a species into a new environment 
disturbs its fixity. Rich soil especially gives rise 
to variations in growth which seem to be new, and 
by repetition become inherently fixed. Sometimes 

12 



David Starr Jordan 




ancestral states are brought about by good soil; 
sometimes (perhaps oftener), also, by starvation; 
new variations oftenest by rich soil and general 
prosperity. There is no evidence of any limit in the 
production of variation through artificial selection^ 
especially if preceded by crossing. Mutations are 
probably due to the sudden appearance of latent 
tendencies in new combinations, producing novel 
effects analogous to new chemical combinations/' 

' ' Mutation is not a period, but a state induced by 
various hereditary and external conditions. It is 
not by any means certain that there is any period 
in the life-history of the species when it is more 
subject to mutation than at other times, other 
conditions being similar. By crossing different 
species we can form more variations and muta- 
tions in half-a-dozen generations than will be 
developed by ordinary variation in a hundred or 
even a thousand generations." 

* ' The La France and some other roses, as well 
as dahlias, calks and many other plants, every 
once in a while throw out, on some particular 

15 



Some Experiments of Luther Burbank 




year, a number of unusual sports in various local- 
ities. This is probably a matter of season, the 
forces outside bringing about parallel mutations. 
The evolution of species is largely dependent on 
crossing the variations contained within it. Forms 
too closely bred soon run out, because generally 
only by crossing does variation appear. It is of 
great advantage to have the parents a certain dis- 
tance apart in their hereditary tendencies. If too 
close together there is not range enough of variety. 
If too far apart, the developed forms are unfitted 
for existence because too unstable. Correlate a 
changes work together to produce the ej^ect of mutattQns, 
Environment efFects a permanent change in species 
by selection of those which fit it or by producing 
changes in individuals which are better equipped 
to survive. Heredity is the sum oj all past environ- 
menty conditions both latent and apparent. Latent 
traits often arise when circumstances make them 
possible. Environment of a lifetime does not 
necessarily or usually appear in another lifetime, 
but continues in the same direction and will strike 



16 



David Starr Jordan 




into the nature of the plant in time. We may 
refer to Emerson's remark on the * baking into 
the picture of the pigment laid down by environ- 
ment/ Selection is 'cumulative environment.' 
Fortuitous variations occur everywhere. They 
come up all the time, from past environments, 
past heredity and present opportunity. No two 
individuals are alike. Where there is a marked 
tendency in one direction, we have the case of a 
persistent efFect of environment. Monstrosities 
are engorgements of force. They are generally 
a thousand times more likely to develop another 
sort of monstrosity than normal individuals are. 
You are likely to get from sports and monstrosities 
either extremes of variance. They do not, however, 
maintain themselves , because heredity pulls back their 
descendants. A wide variance is more easily pulled 
back than a slight variance. There are cases where 
the monstrosity might pull back its species. This 
is more likely to happen if the forces of natural 
or artificial selection were in its favor. There are 
many cases where the variant in minor points is 

17 



Some Experiments of L^uther Burbank 




prepotent and outweighs the original stock. Mon- 
strosities produced by crossing often perpetuate 
themselves as well as the species does." 

" One difficulty with the mutation theory of 
Dr. De Vries, in my opinion, is lack of sufficient- 
ly wide experimentation. Fuller investigations 
will certainly show that the \ sports ' or ' chance ' 
variations comes under the same law as that of 
* fluctuating' variations, mutations being only 
fluctuating variations carried beyond the critical 
point where past fluctuating variations can not 
withstand the accumulated forces without disinte- 
gration, thus bending them in a new direction.'' 

Professor Hubrecht is certainly in error in 
stating that the mean fluctuations can not be car- 
ried into the extreme or * sport ' variations by 
selection. Professor Hubrecht speaks of two diver- 
gent processes, ' fluctuating variations ' and ' muta- 
tions,' which he says: ' Darwin has not sufficiently 
kept separate.' They are not separate; one is only 
a tendency toward the other, and which continued, 
though latent, may, or will, at last become domi- 



18 



David Starr Jordan 




nant, so as to swing the fluctuating variations fully 
out of the old orbit into the * mutation ' or ' sport ' 
condition. Radical changes of environment for 
a series of generations will produce a tendency to 
sport, but hybridization will bring it about far 
more abruptly, and for practical plant or animal 
breeding or for scientific study of all these varia- 
tions, far more satisfactorily/' 

*'The misunderstanding evidently comes from 
not having a clear knowledge of latent and domi- 
nant hereditary forces. A knowledge of these 
explains the whole matter and makes harmony 
between Darwin and Wallace, leaving Professor 
De Vries careful experiments good, but coming 
to different conclusions on the results." 

''Professor Hubrecht also states that 'now for 
the first time — forty years after the appearance of 
the 'Origin of Species — the actual birth of a 
species has been observed by him.' As I have 
produced several good species by hybridization, 
apparently as good as nature herself has produced, 
and as others have done the same by selection 



19 



Some Experiments gJ I^uther Burbank 




alone, the above sentence is hardly true. But as 
before stated, hybridization followed by selection 
is the shortest plan by which valid new species can 
be produced. In other words, the 'period of mu- 
tation ' can be produced at will!'' 

* ' The mutation theory of the origin of species 
seems like a step backward toward the special 
creation theory, and without any facts as yet ade- 
quate to support it as a universal theory, however 
valuable and suggestive the experiments of Dr. De 
Vries may be.'' 

There is a remarkably close analogy between 
hybridization and grafting. Bringing over from 
France a prunus (P. mirobolana var. pissadi), of 
which there was no other specimen in America, 
it was grafted on to the Kelsey plum, a variety of 
Prunus triflorus. The graft itself did not bloom, 
but the presence of the graft brought about in the 
tree a cross off the two species. This is the only 
case known to me in which the graft affected the 
reproductive system of the plant, forming a cross 
between forms which had never crossed. Many 



20 



David Starr Jordan 




hundred descendants of this cross are now hving. 
Darwin acepted with reservations the account of 
the graft hyhrids in potatoes, and there still remains 
some doubt of reliable testimony of the supposed 
act. He also speaks of a now well-known grafts 
hybrid of a yellow and purple cytisus, which is 
perhaps the most remarkable fact in this line on 
record." 




Opuntia ficus-indica and its Hybrid with O. uulgaris^ the Hybrid 
Flower far Larger than either Parent. 



21 



Some 



Experiments of I^uther Bur bank 




DIAGRAM 

Showing the Zone of Life and Parallelism of Resuits in 
Crossing and Grafting. (L. B.) 

Utter refusal to unite under any circumstances, either by /// 
VV\ crossing or grafting. (Outside of zone of possible union. ) // 



Pollen acts as a poison. 

Union partial, mosaic or tem- 
porary; seed rarely produced; 
seedlings generally inherit ten- 
dencies and qualities of one 
parent only; second or later 
generations revert fully. 

Union free; seedlings show 
unbalanced condition, varying 
widely; often unusually vigor- 
ous; best condition for scien- 
tific or natural selection. Good 
qualities can be made perma- 
nent to the race. 

Unite freely; seed of super- 
ior germinating quality pro- 
duced abundantly. Seedlings 
normal with ordinary amount 
of variability. 



Grafts blight and die as if 
poisoned. 

Grafts often form a tempor- 
ary union but are not in a nor- 
mal condition. Avoided by 
nurserymen and planters with 
great care, as results are often 
disastrous to the grower. 

Grafts unite readily but sepa- 
rate under unusual stress — 
drought, overbearing, lack of 
nourishment, etc. Avoided by 
nurserymen and planters. 

Mutative. 
State. ' I 

Large Grafts unite readily, thriving 

Variation, well ; sometimes better than 
when grafted on their own 

\\V// 



Mendelian 
State. 



Ordinary plant life as oftenest Usual Grafts unite and thrive 
met with. Fluctuations, we oftenest see them. 



Self-f ertile ; seed produced, 
but as there are very limited 
opportunities for profitable var- 
iations, this state ultimately 
ends in 



V 



Grafts grow on their own 
roots. 



Extinction. 

All these varying states shade off from one to the other, 
with few hard and fast lines of separation. 



/ 



David Starr Jo 7^ dan 




' ' In some directions the strains of heredity are 
much more unbalanced than in others. An im- 
pulse from outside forces may bring about new 
combinations. This is illustrated by De Vries by 
a ball with many facets, which, if lightly touched, 
will return to its original position, if vigorously 
touched will turn over. Burbank once crossed a 
pole bean {Phaseolus '-cidgaris) with a lima bean 
Phaseolus liinatiis var. inacrocarpiis) . There was 
no visible effect in the appearance of the pod or 
the bean, but, when planted, each bean developed 
a cotyledon, part of one species and part of the 
other. The lima bean represented the end of the 
cotyledon, and was united to the lower part by 
serrated edges ; below was the smaller and striped 
cotyledon of the pole bean. The cotyledons 
finally parted at the joints between the two, the 
upper portion falling off, as is often the case with 
grafts which are uncongenial. The forms were 
tremendously vigorous, but all came back to the 
common pole or horticultural bean after the second 
generation, as though it were an uncongenial graft 

23 



Some Experiments of Euther Burbank 




hybrid, the ahen portion being finally entirely 
rejected. It often happens in grafting, that the 
branch will be united thoroughly at the point of 
grafting, but in great stress, as the overbearing of 
fruit, the grafted portion will separate and entirely 
fallofF/' 

' ' In one sense, hybridization is only a mode of 
grafting, both being a more or less permanent 
combination. The different results from hybridi- 
zation are shown in the diagram below." 

' ' Where the plants are very different, having 
a different line of descent, and consequently differ- 
ent structure, there will be no hydridization at all. 
From this we have every gradation to the point 
where the individuals are very closely alike, and 
here we have scarcely any variation at all in the 
progeny, a condition which favors extinction. 
Again, in grafting, we have every intergradation 
between total inability to unite and absolutely 
perfect blend.'' 

' ' Sometimes a graft strengthens a plant by 
increasing the body of foliage and thus strength- 

24 



David Starr Jordan 



ening the roots. Grafting a Japanese pear on the 
Bartlett pear will give the latter new life through 
the increase in the foliage, which gives material 
for root action and further extension." 

As illustrations of the results of crossing and 
hybridization, the following notes were taken on 
plants in Mr. Burbank's gardens: 

In the beginning of his work Mr. Burbank 
crossed all sorts of beans and had a half acre of 
them. Some climbed to the height of twenty or 
thirty feet, producing all sorts of pods — some with 
pods long and slender and stems so short that the 
pods doubled up on the ground. These forms 
could have been fixed in time, though the varia- 
tions were unusually persistent and very amazing 
in their variety and abundance. 

Crossing the red and white pole bean, two or 
three of the beans grew large and bore striped 
pods, the beans themselves being jet black. From 
this cross many varieties were developed having all 
the colors known in beans. 

The results of selection are often so simple as 



25 



Some Experiments of Luther Burbank 




to form a mathematical rule, as in the case of 
Mendel's peas, which holds good with the tribe 
of peas {Fisuni), but not generally with others so 
far experimented on. At other times they are so 
complicated that to follow them requires the 
highest skill, or may be utterly impossible. 

A rubus (i^. cratoegifolius) from Siberia has 
fruit the size of a large half pea, brownish, seedy 
and tasteless. Hybridizing with the California 
blackberry (i^. vitifolius), some of the hybrids 
have the best qualities of both berries combined, 
and a perfect balance of characters. Out of over 
five thousand second generation hybrid seedlings, 
every one is true to the seed. This refers to the 
Primus blackberry, which is now fully as true a 
species as any classified species of Rubiis. 

The raspberry has been hybridized with a 
strawberry: the results were thornless plants with 
trifoliate leaves looking like a strawberry plant and 
sending out underground stolons like the straw- 
berry. At last, however, the plants send up canes 
three to five feet high bearing panicles of flowers 



26 




more profuse in number than those on either 
parent. After flowering the plant never produces 




Stems of Blackberry-Raspberry Hybrids. 

a berry, the fruit forming a small knob, with no 
effort at maturity. 

In the hybrid of the strawberry and^raspberry, 
the resultant plants bore three or four times as 

27 



Some Experiments of Luther Burbank 




many flowers as the raspberry, seven or eight times; 
as many as the strawberry. 

Tendencies strong in the parent, even though 
for a time latent, usually come out strong in the 
descendants. Ordinary hybrids of forms closely 
related generally form a perfect blend from both 
parents. When the parents are far apart all sorts 
of variations occur, the so-called Mendelian con- 
dition being one phase of the results. 

Hybridizing the iceberg white blackberry with 
the Cuthbert raspberry develops a plant with fol- 
iage and growth midway. About half the plants 
bear fruit which is red like the raspberry, about 
half bear fruit which is white like the iceberg 
blackberry; the quality is midway between the 
blackberry and the raspberry. In the crossed 
fruit (first generation) the flavor is not superior,, 
but it is quite intermediate between blackberry 
and raspberry. The form of the receptacle is 
intermediate. Some of the fruitlets separate at 
the base, but not above. In crossing it makes no 
difference which sex is taken as the male parent; 



28 




J 



Leaves of Blackberry Raspberry Hybrids. 



David Starr Jordan 




it all depends upon the hereditary tendencies of 
the sex. 

Crosses of wild species yield results similar to 
those from cultivated species, but the latter are 
more available. The white blackberry is a wild 
variation crossed with the Lawton for size and 
vigor; the result is a much clearer white than the 
wild one, larger, and very much more productive, 
in these respects fully equal to its staminate parent, 
the Lawton. 

Apples brought up from the south temperate 
zone are entirely confused here, yielding leaves, 
buds, flowers and small apples at various seasons. 
One of these apples in time, however, became 
adapted to the conditions and developed into one 
of the best apples in Mendocino County. 

Animals or plants changed by transference 
from one country to another never quite go back 
to the old conditions, even if placed in them 
again, as hereditary tendencies acquired under 
the new environments, even though latent for 
many generations may be called forth again under 

31 



Some Experiments of Luther Burbank 




favoring conditions. Exceptions seem to be as 
important as the rules in this work. Nature 
leaves so many loopholes that there is almost no 
rule without exceptions. She does not tie herself 
up to any unvarying conditions. Adaptability is 
more important than perseverance." 

A blackberry plant with an immense mass of 
fruit developed from a seedling from the Himal- 
ayas. One plant covers 150 square feet, is 8 feet 
high, and has a bushel or more of fruit. This is 
only a young small plant; when full grown this 
variety is many times larger. 

A purple larkspur reared by Mr. Burbank is 
produced by crossing a native blue with a native 
scarlet, the color being entirely a blend. The 
blackberry was crossed with apples and with all 
the various rosaceous plants. Over five thousand 
plants were produced. The apple-blackberry cross 
came out essentially apples in foliage and growth, 
though raised from blackberry seeds. Only two 
of them ever bloomed, all were thor^nless, one of 
them bearing rose-colored flowers. From the 



32 




Leaves of a Blackberry Hybrid, all grown from Seed of One Plant. 



David Starr Jordan 




mountain ash and blackberry a salmon-colored 
fruit with no thorns and no albumen in the seed 
was developed. A hybrid between the English 
and the black walnut grows fully four times as 
fast as the English walnut; it bears little fruit. 
The seedlings from the fruit produce some 
English, some black, and some hybrid walnuts, 
and not rarely entirely new forms. Crossing often 
brings about great vegetative life at the expense 
of reproductive life, or the reverse. The young 
(second generation) hybrids of the black walnut 
and the English walnut show very great variation 
in their leaves, resembling neither parent. The 
hybrids of the English and California black wal- 
nuts are most rapidly growing trees and unusually 
productive. The first hybrid, of the English with 
the Japanese walnut, /z/^/^z/j- sieboldi, is largely like 
the Japanese in the nuts, but rather more like the 
English in foliage, the second generation being 
very variable as usual. 

By crossing types already crossed, we may often 
bring out the original stock which had been lost 



35 



Some Experiments of I^uther Burbank 




in cultivation. The English walnut has usually 
five leaflets, the black walnut fifteen to nineteen. 
The first generation hybrid has eleven, with a 
fragrance to the leaves that no original walnut has. 
This tendency or trait is just as real as any other. 
The American walnut {Juglans nigra) and the 
California black walnut (/. californicd) are closely 
related species and when hybridized yield fruit of 
very large size and in enormous quantities. 

Descendants of hybrids usually revert to either 
one or the other parent or break up in all direc- 
tions. A cross of the eastern black walnut {^Jug- 
lans nigra) with the California nut (/. californica) 
yields a hybrid which is a very great grower. 
From the seed of this tree a surprising variety of 
mutations are developed, not only resembling 
every possible combination of both parents but 
numerous strange forms. In fact, among about 
two thousand seedlings now alive, almost every 
type or form of walnut foliage may be found. 
There are startling variations in size, form and 
number of leaflets, in the size of the plant, in the 



36 




■^^jtM ^ fL^mm 



#^ m\ S 



Apples — all Seedlings from One Variety, 'The Early Williams,' showing 
ABOUT the Normal Variation of Apple Seedlings. 



David Starr Jordan 




serration of the margins, in the degree of rough- 
ness of the surface, in every feature in which one 
walnut may differ from another. 

Some time since, a hybrid mesembryanthemum 
was developed, and lasted for four years, forming 
an attractive plant with a profusion of white 
flowers. Then all individuals, wherever located, 
died at once, doubtless because conditions were 
adverse : but there was no visible cause of soil, of 
insect pest, of fungus or of climate. These plants 
all died from the root up. A hybrid of petunia 
and nicotiana has abundance of flowers and 
large vigorous leaves, but the roots are inadequate. 
A hybrid red poppy is formed by uniting the 
opium poppy with the oriental poppy. These 
hybrids bloom every day of the year, while the 
blooming season of either parent is only a few 
weeks, but they yield no seed. The seed capsules 
are developed in great variety, some of them four 
to six times as large as the capsules of either 
parent. Others are scarcely thicker than the stem 
which bears them, while others are absolutely and 



39 



Some Experiments of L^uther Burhank 




completely absent. This hybrid poppy is tall and 
generally branches like the opium poppy. It is 
perennial, although its pistillate or seed ancestor 
is a short-lived annual. This red poppy can even 
be divided at the root and multiplied like the 
perennial oriental poppy. These hybrids have 
generally a dark mark at the base of the scarlet 
petals as in the oriental poppy; in some the leaves 
are smoothish and glaucous, as in the opium 
poppy; in most, deep green and hairy, more as 
in the other. Many flowers have their stems 
coalescent with that of the neighboring flower. 

' ' These second generation hybrid poppy plants 
unexpectedly all proved to be perennials, and are 
now making a tremendous growth; the clusters 
of foliage of some of them are fourteen to eighteen 
inches across already. Among this second gener- 
ation hybrid lot of poppies each single plant seems 
to be different from every other plant in the lot 
and strange to say the leaves now resemble not 
only poppy leaves, but celandine, various thistles, 
primroses, turnips, mustards and numerous other 



40 




Seedlings of Japanese Quinces, showing Normal Variations. 



David Starr Jordan 




plants are very closely imitated, showing most 
astounding variations. 




The Original and Improved (Shasta) 
Daisy. 



The Striped amaryllis, vittata, hybridized with 
a Mexican formosissima, has narrow twisted 

petals of a very deep scarlet and nearly plain. 



43 



Some Experiments of Luther Burbank 




The leaves are much narrower than in the vittatdy 
the stalks more slender, and the plants more pro- 
fuse bloomers. 

Hybridizing crinum with amaryllis develops a 
plant with a fine flower but no seeds. Crossing 




Japan Walnut, Result of Cross of the Two. English Walnut. 



the small hardy white calla with a yellow one 
which is not hardy, develops, v/ith selection, a 
hardy yellow calla. 

A crinum from Florida is hardy but not hand- 
some. Crossing this with a handsome crinum 
from Mexico, the plants were selected for those 
which should be both hardy and handsome. The 



44 



David Starr Jordan 




desired qualities of the two species have been com- 
bined and other valuable new qualities incidentally 
developed as regeneration and selection proceeded. 

In hybridizing callas, the yellow ones with the 
white, to form a hardy yellow race, some of the re- 
sultant plants have pale flowers, some light yellow, 
and those chosen are made deep yellow by selec- 
tion from second and later generations. Both 
parent plants in this case have leaves blotched with 
white, and this is found in all the descendants. 

Hybridizing the wild flower, Erysimum arkan- 
sanum, which is yellow, with a native wild white 
species, resulted in the first generation a perfect 
blend of yellow and white; with a second gener- 
ation the species separate completely, about five 
per cent of those examined being yellow, the 
other ninety-five per cent white ; white dominant. 
With a hybrid Tfialictrum, seed pods are devel- 
oped more abundantly than with either parent, 
but the seeds are not produced. 

We may expect variations in form, size, color, 
quality, fragrance, vigor or any other characteristic. 

47 



Some Experiments by I^uther Burbank 




To get variation in any one direction is to 
open the door to anything else. Hybridizing the 
Japanese quince with the common quince, we 
have large-leaved seedlings which look quite 
different from the parent (common quince). The 
final result is a seedling looking like the Japanese 
quince, without the power of continued growth 
(too wide a cross to blend permanently or pro- 
fitably). 

Some of the black raspberries when hybridized 
with some of the blackberries usually die when 
the time comes to bear fruit. Many h3^brids 
perish under the stress of reproduction. The 
Amaryllis vittata is now eight to eleven inches 
across, being nearly four times as broad as before 
the work of selection for size was begun, and 
with vigor and freedom of growth and bloom 
amazingly increased. On a strip of poor land it 
grows very small, with narrow leaves and slender 
flowers, but on the same poor land some of the 
hybrid variants grow very large and pay no atten- 
tion to the soil. A variant of Ainpelopsis quinquefolia 

48 



/ 



Hybrid Mesembryanthemum. 



David Starr Jordan 




has very large leaves, highly colored in the fall, 
but no fruit. Mimulus tigrimis of Europe has 
very many variations. Its flowers are yellow, with 




Sample of Hybrid Poppies. 



patches of orange and other colors. When crossed 
with some of our native species, the seedlings are 
greatly improved in all respects, even in blooming, 
yet rarely produce seeds. 



51 



Some Experiments of Luther Burbank 




It is generally much easier to develop variations 
in seedlings from variegated flowers than from 




Sample Leaves of Two Species of Boc- 
conia, showing one of thousands of 
Cases of Great Variation in Foliage 
IN Closely Related Species. 



those of solid color (the variegation shows a lack 
of complete amalgamation). A double mimulus 
is formed of the hose-en-hose sort. One hybrid 



52 




Leaves from Hybrid Poppies, showing unusual variation in foliage even for 
second generation hybrids. Blossoms vary about as much as the leaves — the 
habits of the plants also. These are an average random selection from^about two 
thousand second generation seedlings. 



David Starr Jordan 




poppy produces an abortive flower inside the cap- 
sule. All seedlings always vary more or less. 
With the same parent, one fruit may be two and 




Capsules of Second Generation Hybrid Poppies, showing series of vari- 
ations from complete absence of capsules to capsules of unusual size and to 
double capsules of unusual size. These selected at random from about two 
thousand plants. The individual plants which produce these types generally 
follow them in all the capsules. 

one half or more times the diameter of the other, 
of a different color, flavor or differing in almost 
all respects. ' ' There is no prepotency of male or 
female as such. Prepotency depends wholly on 



55 



Some Experiments of I^uther Burbank 




heredity. We can not rely on the stoneless types 
being prepotent, but a certain number of trees 
producing stoneless fruit usually come from cross- 
ing them with those having stones. The pre- 
potency to produce a stone, or a half stone, having 
been more thoroughly fixed by ages of stone- 
producing trees, will perhaps be about ninety-nine 
times out of one hundred. But other things 
being equal, there is absolutely no balance in favor 
of either sex. This may be set down as fixed.'' * 

With plum-almond crosses there is every kind 
of variation in the flowers. Some have all 
stamens, some have many petals or none, some 
never open, and some have pistils only. 

The Climax plum is a cross of the bitter, flat, 
tomato-shaped Chinese plum, Prunus simoni, and 
the Japanese plum, Prunus triflora. The Chinese 
plum produces almost no pollen; hardly a grain 
of it is known, not more than one could put in 
his eye without feeling it; but the whole fruit 
shipping industry of the world has been changed 
by this hybrid plum (Climax) produced by it. 

56 




Original Wild Stoneless Plum at the Top, and Fourteen of its Seedlings 

WHEN crossed WITH THE FRENCH PrUNE BeLOW, ABOUT ONE-FOURTH SiZE. 



David Starr Jordan 




With many crosses of many things it is certain 
that forms of great importance will come out 
every year, though never in profusion. 

In developing a spineless cactus for stock-feed- 
ding, selections were made from the three hard 
northern species, Opuntia rafinesquii, O. mesacantha 
and O. vulgaris, the latter the common prickly 
pear; these were crossed with O. tuna, of South- 
ern California, ficus indica, from Alba, Spain, and 
with a small opuntia from Central America, almost 
thornless. 

The cactus of all species has smooth cotyledons, 
but the first bud is covered with thorns. These 
thorns have also been eliminated by selecting the 
smoothest individual seedlings without crossing. 
Crossing in this case generally interrupts the 
process, as it brings out well-fixed ancestral 
traits, but later, to combine the best qualities of 
several species, crossing and selection must be 
resorted to. Examples seen were shoots of the 
original stock, prickly; the second generation, 
slightly prickly; the third, without thorns; and 

59 



Some Experiments of Luther Burbank 




later the spicules even within the substance of the 
cactus have been removed so as to make the cactus 
very excellent food for cattle. This will have very 
great value in the arid regions. Some cacti lose 
the thorns on the plant but retain them on the 
fruit ; others vice versa. By crossing and extensive 
and intensive selection a cactus may be improved 
in various ways besides being deprived of thorns 
and of the internal spicules in six or less gener- 
ations; these, by means of cuttings, may be 
multiplied rapidly to any extent, but the process, 
to be complete, generally takes longer. This 
thornless cactus should prove of very great value 
in the development of desert regions as Arizona 
or Sonora, as the quantity of food produced per 
acre is enormous. Its value is being already 
(1908) fully tested on a large scale near Indio, 
in California, and in the state of Victoria in 
Australia. It is evident that the thornless cactus 
cannot be expected to flourish as a wild plant on 
the desert, for cattle and other browsing animals 
would devour it root and branch. Its effectiveness 



60 











( 








Plum COT — an Absolutely New Fruit 


Original and Improved Beach Plum. 


# ^ # 

4# ^ ^ 



Ten Varieties of Plums grown from the Seed of the Burbank Plum crossed 
WITH THE Apricot Plum, showing Variations. 



David Starr Jordan 




is as a forage plant to be cut and thrown to cattle 
as green fodder. For this purpose it is extraor- 
dinarily abundant as to quantity, and at the same 
time most excellent as to quality, having a high 




Thallus and Fruit of Spineless Cactus. 

nutritive value, exceeding in this respect most or 
all of the grasses. 

Incidentally, in this connection, the edible 
fruit of the Opuntia ficus-indica or '^Barbary Fig,'' 
which has been long cultivated in Southern Eur- 
ope and Northern Africa has been greatly im- 
proved under selection. This plant was originally 
a native of Tropical America, but has been long 
grown in gardens of Spain, Italy, Morocco and 

63 



Some Experiments oj Euther Burbank 




Algiers, and the yellow and red ' 'figue de barbare' ' 
may often be found in the Paris markets. 




Bed of Seedlings from Spineless Cactus, showing here and there Reversion 
TO THE Original Spinous Form. . 

Burbank has now (1908) when this interpo- m 
lated page is written, upwards of 500 kinds of ^ 
edible cactus, with fruit yellow, crimson and 



64 




I 



\ 



David Starr Jordan 




green, some with the flavor of Rockford cant- 
eloupe, others with the characteristic quahty of 
peach, plum and pomegranate. These fruits are 





Thornless Opuntia, with Joints Growing Out from the Fruit. 



extremely grateful to the palate. They are borne 
in enormous profusion. They are ripe at all 
times of the year, and they bear transportation 

67 . 



Some Experiments of L.uther Burbank 




perfectly. All they lack is a- reduction in the too 
large number of the small and stony seeds. When 
this change is made as can be readily done in a 
few more selected crossings, no fruit of California 
shows so much promise as this. As every new 
seedling is a new variety as is the case with the 
apple and the potato there is no visible limit to the 
possible range of improvement in the flavor of 
fruit or in abundance of desired crop. 'The 
dehorning' of the cactus is perhaps economically 
Mr. Burbank' s greatest achievement. Next to 
this in time will rank the enlargement and per- 
fection of the cactus fruit. 

The Bartlett plum is a remarkable creation. A 
plum in all respects, but with the exact flavor of a 
Bartlett pear, and the same granular texture. The 
*rice seed' plum has extremely small seeds. The 
stoneless plum is a cross of the French prune with 
a wild plum having the stone almost eliminated 
by a fortuitous variation. The result thus far is 
a great number of stoneless plums of good size, 
but in flavor inferior to the best cultivated ones. 



68 




I 

L 



David Starr Jo r d a n 




These are being crossed again to improve the 
flavor, and new selections made. 

Crossing the Japan and the New England 
chestnut {Castanea japonica and C. americand), the 
trees, leaves, growth and nuts are midway; second 
generation and later generations as usual show 
more varied combinations and variations. To 
breed the burrs off from chestnuts is dangerous, 
because it allows the birds to get in at the nuts. 
The burr is originally intended to keep off the 
birds. In developing his perfect variety of the 
Persian (often called English) walnut {Juglans 
regia), the shell was made too thin, so that the 
birds could break in. It was necessary to make 
new selections and crossings to thicken the shell 
and still retain its other superior qualities. 

The Pierce grape was a bud sport from the 
Isabella, producing much larger fruit. This bud 
sport remains constant. All the seedlings even 
from it are similar to the Pierce grape, following 
the bud sport {Pierce) and not reverting to the 
real parent form of the Isabella. Some ripen 



71 



Some Experiments of Luther Burbank 




early, some late; some are pale, and some are 
black; but all resemble the Pierce more than the 
Isabella. Cultivating a choke cherry, the seeds all 
from one parent tree, many variations are found, 
although the soil in which they are placed is uni- 
form. Among them was found one variant less 
bitter than usual ; others earlier or later ripening 
and with larger or smaller fruit or leaves, and 
an almost bewildering number and variet}^ of 
other variations. A peach-almond cross often de- 
velops a tree as large as ten peach trees or almond 
trees of the same age. Sometimes a similar cross 
with different individuals of the same species will 
produce opposite or totally different results, owing 
to past heredity, either recent or far back. Crosses 
are sometimes more vigorous than either parent 
and more than any descendant, but other cases are 
just the reverse. The more variant crosses are 
often less vigorous, and sometimes yield seedlings 
that can not exist. Sometimes all die in the fruit- 
ing season. A peach named 'Quality' is one of 
the best peaches extant — a cross of the Muir and 

72 




Joint of Opuntia Cut in Two and Planted Bottom Up. Fruits 
OF Opuntia, the Larger Planted Bottom Up. 



David Starr Jordan 




the Crawford. A cross of the nectarine and peach 
also produces variant types of value. In some 
hybrids of petunia and tobacco, the roots fail 
while the tops may be of unusual vigor. These 
individuals can only be kept alive for any length 
of time by grafting, another instance — if other 
were needed — of the parallelism of crossing and 
grafting. 

character may be latent through many 
generations or centuries, appearing when the right 
cross brings it out, or it may appear under espe- 
cially favorable or peculiar conditions of growth.'* 
The essential of Burbank's method may be 
here briefly restated. In the formation of all 
races or breeds of animals or plants we may have 
the following stages : — 

1. Unconscious selection with more or less 
complete isolation of the chosen forms. 

2. Conscious selection of the most desirable 
individuals. 

3. Conscious selection directed towards definite 
or special ends. 



75 



Some Experiments of I^uther Burbank 




4. Crossing with other races or other species, 
to increase the range of variation or to add or 
combine certain desirable quahties or to ehminate 
others which are not desirable. This must be 
accompanied by segregation or isolation, and it 
must be followed by conscious selection which 
must be directed towards definite end. On this 
last series of processes all animal breeding and all 
plant breeding as a fine art must depend. 

In the beginning men were satisfied with 
strawberries as strawberries. If they transplanted 
them, they took what they found. Later the 
best strains were kept together, and at last through 
purposeful crossing, the fine art of making new 
kinds of strawberries was developed. The same 
method applies to any plant or animal. It might 
apply to man if selection and segregation were 
part of our scheme of society. Unfortunately for 
this plan, the best cannot be selected or segre- 
gated, fortunately, perhaps, as the control of one's 
own afFairs develops man's best quality, personal 
initiative. In that regard, freedom may be a 

76 



David Starr Jordan 




better end in human development than any type 
of physical perfection. 

According to Burbank, the facts of plant life 
demand a kinetic theory of evolution, a slight 
change from Huxley's statement that 'matter is a 
magazine of force/ to that of matter being force 
alone. The time will come when the theory of 
ions will be thrown aside and no line left between 
force and matter. We can not get the right per- 
spective in science unless we go beyond our senses. 
A dead material universe moved by outside forces 
is in itself highly improbable, but a universe of 
force alone is probable, but requires great effort to 
make it conceivable, because we must conceive 
it in the terms of our sense experience." 

Whether we accept this or not, whether or 
not indeed we can conceive what it means, this 
view of life, which Burbank shares with many 
other philosophers, opens to us many new vistas 
of thought, and what means more for the progress 
of knowledge, it suggests to us many new avenues 
of experimentation. 



77 



Some Experiments by Luther Burbank 




Luther Burbank, while primarily an artist, is, 
in his general attitude, essentially a man of science. 
Academic he doubtless is not, but the qualities we 
call scientific are not necessarily bred in the acad- 
emy. Science is human experience tested and 
set in order. Within the range of his profession 
of moulding plant life, Mr. Burbank has read 
carefully, and thought carefully, maturing his own 
generalizations and resting them on the basis of 
his own knowledge. Within the range of his 
own experience he is an original and logical 
thinker, and his conclusions are in general most 
sound. He is not a physiologist, still less a histol- 
ogist, and the phenomena of heredity as shown in 
cell-division and cell-multiplication, he has not 
studied for himself. The researches of Weismann 
and those suggested by his theories of heredity 
Burbank has given little attention to, and he has, 
therefore, a confidence in the inheritance of ac- 
quired characters, such as effects of environment, 
which most biologists of today do not share. On 
the other hand, many of the best of them would 



78 



David Starr Jordan 




fully agree with Burbank. In his field of the 
application of our knowledge of heredity, selec- 
tion, and crossing to the development of plants, 
he stands unique in the world. No one else, 
whatever his appliances, has done as much as 
Burbank, or disclosed as much of the laws govern- 
ing these phenomena. Burbank has worked for 
years alone, not understood and not appreciated, 
at a constant financial loss, and for this reason — 
that his instincts and purposes are essentially those 
of a scientific man, not of a nurseryman or even 
of a horticulturist. To have tried fewer experi- 
ments and all of a kind likely to prove economi- 
cally valuable, and finally to have exploited these 
as a nurseryman, would have brought him more 
money. In his own way, Burbank belongs in the 
class of Faraday and the long array of self-taught 
great men who lived while the universities were 
spending their strength on fine points of grammar 
and hazy conceptions of philosophy. 'His work 
is already an inspiration to botanists as well as 
horticulturists, opening a new line of search in 



79 



Some Experiments of Luther Burbank 



heredity, as well as a new field for economic 
advance. Already his methods are yielding rich 
results in the hands of others. We shall by such 
means find much more than we now know of the 
evolution of organisms, while the improvement 
of organisms for the use and pleasure of man is 
yet in its infancy. 

Scientific men belong to many classes; some 
observe, some compare, some think, and some 
carry knowledge into action. There is need for 
all kinds and a place for all. With a broader 
opportunity, Burbank could have done a greater 
variety of things and touched life at more points; 
but, at the same time, he would have lost some- 
thing of his simple intensity and fine delicacy of 
touch — things which schools do not always give 
and which too much contact with men sometimes 
takes away. 

Great men are usually men of simple, direct 
sincerity of character. These marks are found in 
Burbank. As sweet, straightforward, and as 
unspoiled as a child, always interested in the 



80 



David Starr Jordan 




phenomena of Nature, and never seeking fame 
or money or anything else for himself. If his 
place is outside the temple of science, there are 
not many of the rest of us who will be found fit 
to enter. 




Eleagnus longipes^ Japanese Goumberry, 
Improved by Selection. 



81 



Scientific Aspects of Luther 
Burbank's Work . 

By Vernon Lyman Kellogg 



Vernon y m a n Kellogg 





R. BURBANK has so far not for- 
mulated any new or additional 
laws of species-change, nor do his 
observations and results justify any 
such formulation, and we may 
rest in the belief that he has no new fundamental 
laws to reveal. He has indeed the right to formu- 
late, if he cares to, some valuable and significant 
special conclusions touching certain already recog- 
nized evolution factors, in particular, the influence 
on variability of the two long-known variation- 
producing factors of hybridization and modifica- 
tion of environment. His reliance on the marked 
increase in variability to be got after a crossing in 
the second and third generations over that obvious 
in the first will come as a surprise to most men 
first getting acquainted with his work. He has 
got more starts for his new things from these gen- 
erations than in any other way. He is wholly clear 
and convinced in his own mind as to the inheri- 
tance of acquired characters ; ' acquired characters 



85 



Scientific Aspects of Luther Burbank V Work 




are inherited .or I know nothing of plant life/ he 
says; and also convinced that the only unit in 
organic nature is the individual, not the species; 
that the so-called species are wholly mutable and 
dependent for their apparent fixity solely on the 
length of time through which their so-called 
phyletic characters have been ontogenetically re- 
peated. He does not agree at all with de Vries 
that mutations in plants occur only at certain peri- 
odic times in the history of the species, but rather 
that, if they occur at all, they do so whenever the 
special stimulus derived from unusual nutrition or 
general environment can be brought to bear on 
them. He finds in his breeding work no prepo- 
tency of either sex as such in inheritance, though 
any character or group of characters may be pre- 
potent in either sex. He believes that no sharp 
line can be drawn between the fluctuating or so- 
called Darwinian variations and those less usual, 
large, discontinuous ones called sports. Ordinary 
fluctuating variation goes on under ordinary con- 
ditions of nutrition, but with extraordinary envir- 



86 



Vernon y m u n Kellogg 




onmental conditions come about extraordinary 
variation results, namely, discontinuous, sport or 
mutational variation. These variations are the 
effects of past environment also, having remained 
latent until opportunity for their development 
occurs. Starvation causes reversions, but rever- 
sions can also be produced by unusually rich nutri- 
tion. New variations are developed most often, 
as far as environmental influences go, by rich soil 
and generally favorable conditions. So-called new 
qualities are usually, if not always (the fact may 
sometimes not be obvious), simply new combina- 
tions of old qualities, both latent and obvious. To 
get a new and pleasing odor it may often be sufli- 
cient simply to lose one bad element in an old 
odor. So one might go on for some pages with 
specific conclusions or deductions reached by 
Burbank on a basis of experience. But it is true 
that he has at his command the knowledge of no 
new fundamental scientific principles to give him 
advantage over us. And yet none of us has done 
what Burbank has been able to do, although many 



87 



Scientific Aspects of I^uther Burbank' s Work 




of us have tried. What then is it that Burbank 
brings to his work of modifying organisms swiftly 
and extremely and definitely that others do not ? 

To answer this it will be advisable to analyze, 
in general terms, at least, the various processes 
which either singly, or in combinations of two or 
three, or all together, are used by Mr. Burbank 
in his work. We may roughly classify these 
processes and means. First, there is the importa- 
tion from foreign countries, through many cor- 
respondents, of a host of various kinds of plants, 
some of economic value in their native land and 
some not, any of which grown under different 
conditions here may prove specially vigorous or 
prolific or hardy, or show other desirable changes 
or new qualities. Among these importations are 
often special kinds particularly sought for by 
Burbank to use in his multiple hybridizations; 
kinds closely related to our native or to already 
cultivated races which, despite many worthless 
characteristics, may possess one or more particular, 
valuable ones needed to be added to a race already 



88 



Vernon Lyman Kellogg 




useful to make it more useful. Such an addition 
makes a new race. 

Second, the* product of variations, abundant 
and extreme, by various methods, as (^) the 
growing under new and, usually, more favorable 
environment (food supply, water, temperature, 
light, space, etc.) of various wild or cultivated 
forms, and (/^) by hybridizations between forms 
closely related, less closely related and, finally, as 
dis-similar as may be (not producing sterility), this 
hybridizing being often immensely complicated 
by multiplying crosses, /. <?., the offspring from 
one cross being immediately crossed with a third 
form, and so on. These hybridizations are made 
sometimes with very little reference to the actual 
useful or non-useful characteristics of the crossed 
parents, with the primary intention of producing 
an unsettling or instability in the heredity, of 
causing, as Burbank sometimes says, ' perturba- 
tion ' in the plants, so as to get just as wide and 
as large variation as possible. Other crosses are 
made, of course, in the deliberate attempt to 



89 



Scientific Aspects of Luther But bank's Work 




blend, to mix, to add together, two desirable 
characteristics, each possessed by only one of the 
crossed forms. Some crosses are made in the 
attempt to extinguish an undesirable characteristic. 

Third, there is always immediately following 
the unusual production of variations, the recogni- 
tion of desirable modifications and the intelligent 
and efFective selection of them, /. e., the saving of 
those plants to produce seed or cuttings which 
show the desirable variations and the discarding 
of all the others. In Burbank's gardens the few 
tenderly cared for little potted plants or carefully 
grafted seedlings represent the surviving fittest, 
and the great bonfires of scores of thousands of 
uprooted others, the unfit, in this close mimicry 
of Darwin and Spencer's struggle and survival in 
nature. 

It is precisely in this double process of the 
recognition and selection of desirable variations 
that Burbank's genius comes into particular play. 
Right here he brings something to bear on his 
work that few other men have been able to do. 



90 



V e r n n y m a n Kellogg 




It is the extraordinary keenness of perception, the 
dehcacy of recognition of desirable variations in 
their (usually) small and to most men impercepti- 
ble beginnings. Is it a fragrance that is sought? 
To Burbank in a bed of hundreds of seedling 
walnuts scores of the odors of the plant kingdom 
are arising and mingling from the fresh green 
leaves, but each, mind you, from a certain single 
seedling or perhaps from a similar pair or trio. 
But to me or to you, until the master prover 
points out two or three of the more dominant 
single odors, the impression on the olfactories is 
simply (or. confusedly) that of one soft elusive 
fragrance of fresh green leaves. Similarly Bur- 
bank is a master at seeing, and a master at feeling. 
And besides he has his own unique knowledge of 
correlations. Does this plum seedling with its 
score of leaves on its thin stem have those leaves 
infinitesimally plumper, smoother or stronger, or 
with more even margins and stronger petiole or 
what not else, than any other among a thousand 
similar childish trees ? Then it is saved, for it will 



91 



Scientific Aspects of Luther Burbank' s Work 




bear a larger, or a sweeter, or a firmer sort of 
plum, or more plums than the others. So to the 
bonfires with the others and to the company of 
the elect with this ' fittest ' one. Now this recog- 
nition, this knowledge of correlations in plant 
structure, born of the exercise of a genius for 
perceiving through thirty years of opportunity for 
testing and perfecting it, is perhaps the most 
important single thing which Burbank brings to 
his work that cither men do not (at least in such 
unusual degree of reliability). Enormous indus- 
try, utter concentration and single-mindedness, 
deftness in manipulation, fertility in practical re- 
source, has Burbank — and so have numerous 
other breeders and experimenters. But in his 
perception of variability in its forming, his recog- 
nition of its possibilities of outcome, and in his 
scientific knowledge of correlations, a knowledge 
that is real, for it is one that is relied on and built 
on, and is at the very foundation of his success^ 
Burbank has an advantage of true scientific char- 
acter over his fellow workers, and in it he makes 



92 



Vernon 



y m a n Kellogg 




a genuine contribution to sci- 
entific knowledge of plant bi- 
ology, albeit this knowledge 
is so far only proved to be 
attainable and to exist. It is 
not yet exposed in its details 
and may never be, however 
unselfish be the owner of it. 
For the going to oblivion of 
scientific data of an extent and 
value equivalent, I may esti- 
mate roughly, to those now 
issuing from any half dozen 
experimental laboratories of 
variation and heredity, is the 
crying regret of all evolution 
students acquainted with the 
situation. The recently as- 
sumed relations of Mr. Bur- 
bank to the Carnegie Insti- 
tution are our present chief 
hope for at least a lessening 




Hybrid Walnut ' Par- 
adox," Juglans regia and 
/. Californica. Each One 
Year Old, Same Parents 
AND Same Nurture. One 
500 Size of Other. 



of this loss. 



93 



Scientific Aspects of l^uther Burbank ' s W irk 




But let us follow our saved plum seedling. 
Have we now to wait the six or seven years before 
a plum tree comes into bearing to know by actual 
seeing and testing what new sort of plum we have ? 
No; and here again is one of Burbank' s contribu- 
tions (not wholly original to be sure, but original 
in the extent and perfection of its development) 
to the scientific aspects of plant-breeding. This 
saved seedling and other similar saved ones (for 
from the examination of 20,000 seedlings, say, 
Burbank will find a few tens or even scores in 
which he has faith of reward) will be taken from 
their plots and grafted on to the sturdy branches of 
some full-grown vigorous plum tree, so that in the 
next season or second next our seedling stem will 
bear its flowers and fruits. Here are years saved. 
Twenty, forty, sixty, different seedlings grafted 
on to one strong tree (in a particular instance 
Burbank had 600 plum grafts on a single tree ! ) ; 
and each seedling-stem certain to bear its own kind 
of leaf and flower and fruit. For we have long 
known that the scion is not materially influenced 

94 



Vernon y m a n Kellogg 




by the stock nor the stock by the scion ; that is not 
modified radically, although grafting sometimes 
increases or otherwise modifies the vigor of growth 
and the extent of the root system of the stock. 



One of the Stoneless Plums (Center) and Two of its Parents. 
On the right hand is the common French prune. 

If now the fruit from our variant seedling is 
sufficiently desirable ; if it produces earlier or later, 
sweeter or larger, firmer or more abundant, plums, 
we have a new race of plums, a 'new creation' to 
go into that thin catalogue of results. For by 
simply subdividing the wood of the new branch, 
/. e,y making new grafts from it, the new plum can 



95 



Scientific Aspects of l^uther Burbank' s Work 




be perpetuated and increased at will. Simple, is it 
not ? No, it is anything but that in the reality of 
doing it; but in the scientific aspects of it, easily 
understandable. 

Perhaps it may not be amiss to call attention to 
what must be the familiar knowledge of most of 
us, and that is the fact that many (probably most) 
cultivated plants must be reproduced by division, 
that is by cuttings, buds or grafts, and not by seeds, 
in order to grow 'true.' For a piece of a cultiva- 
ted plant will grow out to be very much like the 
individual it was cut from, but the seeds will not, 
in most cases, reproduce faithfully the parents, but 
will produce a very variable lot of individuals, 
most of them strongly reversionary in character. 
Grow peach trees from the stones of your favorite 
peach and see what manner of peaches you get; 
but if you want to be sure of more peaches like 
the ones you enjoy, graft scions from your tree on 
to other trees. Indeed one of the plant-breeder's 
favorite methods of making a start for new things, 
of getting the requisite beginning wealth and 



96 



Vernon L. y m a n Kellogg 




eccentricity of variation, is to grow seedlings, 
especially from cross-bred varieties. Burbank will 



^^1^ 1 









Zea Mays, (Cuzco Corn). Parent of Indian Corn. Female flower 
at base of each tassel and protected by a leaf. Male flower below 5 this 
prevents self fertilization. 



give you a thousand dollars for a pin-ch of horse- 
radish seed. Sugar-cane seed is needed. The amel- 
ioration of many kinds of fruit and flowers and 



97 



Scientific Aspects of huther Bur bank's Work 




vegetables is checked, because in our carelessness 
we have allowed these kinds to get into that condi- 
tion of seedlessness which almost all cultivated races 
tend toward when grown from cuttings. In our 
oranges and grape-fruit and in a score of other 
fruits, the elimination of seeds is exactly one of 
the modifications we have bred and selected for, 
in order to make the fruits less troublesome in their 
eating. But when we lose the seeds entirely of a 
whole group of related plant kinds we may find 
ourselves, as we have found ourselves actually in 
many cases, at the end of our powers of ameliora- 
tion of these plant sorts. Burbank believes that 
the very fact that plants when grown asexually 
always sooner or later lose their power to produce 
seeds is almost sufficient proof (if such proof is 
needed) that acquired characters are transmitted. 

Another of Burbank' s open secrets of success 
is the great range of his experimentation — nothing 
is too bold for him to attempt, the chances of fail- 
ure are never too great to frighten him. And 
another secret is the great extent, as regards 



98 



Vernon L, y m a n Kellogg 




material used, of each experiment. His beds of 
seedlings contain hundreds, often thousands, of 
individuals where other men are content with hun- 




Leaves of Hybrid Blackberry Plants of the Same Parentage 

dreds. Another element in his work is his prodi- 
gality of time. Experiments begun twenty years 
ago are actually still under way. 

In all that I have so far written, I have pur- 
posely kept to general statements applicable to 
Burbank's work as a whole. My readers might 

99 



Scientific Aspects of Luther Burbank ' s W ork 




be more interested, perhaps, to have some illustra- 
tions of the application of various processes of 
making new sorts of things, some analytical ac- 
count of the history of various specific *new crea- 
tions,' but considerations of space practically for- 
bid this. Just a few briefly described examples 
must suffice. More than is generally imagined, 
perhaps, Burbank uses pure selection to get new 
things. From the famous golden orange colored 
California poppy {Eschoitzia) he has produced a 
fixed new crimson form by selection alone. That 
is, noticing, somewhere, sometime, an Eschoitzia 
individual varying slightly redder, he promptly 
took possession of it, raised young poppies from 
its seeds, selected from among them those varying 
in a similar direction, raised new generations from 
them and so on until now he who wishes xTiay 
have his California poppies of a strange glowing 
crimson for the price of a little package of seed, 
where formerly he was perforce content with the 
golden orange. For me the golden orange suf- 
fices, but that does not detract from my eager 

100 



Vernon 1^ y m a n Kellogg 




in terest in the flower-painting methods, of Mr. 
Burbank. Even more striking a result is his blue 
Shirley poppy, produced also solely by repeated 




I 

Hybrid Chestnut in Fruit, Six Months Old. 

selection from the crimson field poppy of Europe. 
*'We have long had various shades of black and 
crimson and white poppies, but no shade of blue. 
Out of 200,000 seedlings I found one showing a 
faintest trace of sky blue and planted the seed from 

101 



Scientific Aspects of I^uther Burbank V Work 




it, and got next year one pretty blue one out of 
many thousand, and now I have one almost pure 
blue/' 

But another brilliant new poppy was made in 
a different way. The pollen of Papaver pilo- 
sum, a butter-colored poppy, was put on the pistils 
of the Bride, a common pure white variety of 
Papaver somniferum (double), and in the progeny 
of this cross was got a fire-colored single form. The 
character of singleness was common to the ances- 
tors of both parents, the character of fire color in 
the lineage of somniferum only, although the red 
of the new form is brighter than ever before known 
in the somnifera series. Both characteristics were 
absent (or rather latent) in both parents. And 
yet the perturbing influence of the hybridization 
brought to the fore again these ancestral characters. 
The foliage of this fire poppy is intermediate in 
type between that of the two parents. 

The history of the stoneless and seedless plum, 
now being slowly developed by Burbank, shows an 
interesting combination of selection, hybridization 



102 



Vernon y m a n Kellogg 




California Poppy {Eschscholtzia) Rendered Bright Crimsonas a Result 
OF Selection only, without Crossing. 



He crossed this wild species with the French 
prune; in the first generation he got most indivi- 
duals with whole stones, some with parts of a 
stone, and even some with no stone. Through 



103 



Scientific Aspects of Luther Bur bank' s Work 




three generations he has now carried his Hne by 
steadily selecting, and the percentage of no-stone 
fruits is slowly increasing, while quality, beauty 
and productiveness are also increasing at the same 
time. 

The plum-cot is the result of crossing the 
Japanese plum and the apricot. The plum-cot, 
however, has not yet become a fixed variety and 
may never be, as it tends to revert to the plum and 
apricot about equally, although with also a ten- 
dency to remain fixed, which tendency may be 
made permanent. 

Most of Burbank's plums and prunes are the 
result of multiple crossings in which the Japanese 
plums have played an important part. Hundreds 
of thousands of seedlings have been grown and 
carefully worked over in the twenty years of ex- 
perimenting with plums, and single trees have 
been made to carry as many as 600 varying seedling 
grafts. The Bartlett plum, cross of the bitter 
Chinese Simoni and the Delaware, itself a Simoni 
hybrid, has the exact fragrance and flavor of the 

104 



Vernon L, y m a n Kellogg 




Bartlett pear. The Climax, a successful shipping 
plum, is also a cross of the Simoni and the Japan- 




Rhodanthe naglesi^ a Rose-Colored Everlasting Flower Improved 
IN Size and Color by Selection Only. 

ese triflora. This Chinese Simoni produces almost 
no pollen, but few grains of it ever having been 
obtained. But these few grains have enabled Bur- 
bank to revolutionize the whole plum shipping 



105 



Scientific Aspects of I^uther Burbank' s Work 




industry. The sugar prune, which promises to 
supplant the French prune in Cahfornia, is a 
selected product of a second or third generation 
variety of the Petite d'Agen, a somewhat variable 
French plum. 

Next in extent probably to Burbank's work 
with plums and prunes is his long and successful 
experimentation with berries. This has extended 
through twenty-five years of constant attention, 
has involved the use, in hybridizations, of forty 
different species of Rubus, and has resulted in the 
origination of a score of new commercial varieties, 
mostly obtained through various hybridizations of 
dewberries, blackberries and raspberries. Among 
these may specially be mentioned the Primus, a 
hybrid of the western dewberry {R, ursinus) and 
the Siberian raspberry {R. cratagifolius), fixed in 
the first genereration, which ripens its main crop 
before most of the standard varieties of raspberries 
and blackberries commence to bloom. (Mr. Bur- 
bank does not recommend this for general cultiva- 
tion; the ThenomenaF and Himalaya are better.) 

106 



Vernon L, y m a n Kellogg 




In this Primus berry, we have the exceptional in- 
stance of a strong variation, due to hybridization. 




Heuchera Leaves made Crested by Selection of 
Varying Seedlings. 



breeding true from the time of its first appearance. 
It usually takes about six generations to* fix a new 
variety, but like de Vries's evening primrose muta- 
tions, the Primus berry is a fixed new form from 



107 



Scientific Aspects of I^uther Burbank V Work 




the time of its beginning. An interesting feature 
of Mr. Burbank' s brief account, in his 'New Cre- 
ations' catalogue of 1894, of the berry experimen- 
tation, is a reproduction of a photograph showing 
*'a sample pile of brush 12 ft. wide, 14 ft. high, 
and 22 ft. long, containing 65,000 two and three- 
year-old seedling berry bushes (40,000 blackberry 
X raspberry hybrids and 25,000 Shaffer X Gregg 
hybrids) all dug up with their crop of ripening 
berries." The photograph is introduced to give 
the reader some idea of the work necessary to pro- 
duce a satisfactory new race of berries, ''Of the 
40,000 blackberry X raspberry hybrids of this kind 
'Phenomenal' is the only one now in existence. 
From the other 25,000 hybrids, two dozen bushes 
were reserved for further trial." 

An astonishing result of the hybridization 
between the black walnut, Juglans nigra, used as the 
pistillate parent, and the California walnut, /. 
calijornica^ staminate parent, are walnut trees which 
grow with such an amazing vigor and rapidity 
that they increase in size at least twice as fast as the 



108 




combined growth of both parents. Many tremen- 
dous growers are got in the first generation, but in 
the second there are included some of the most 
rapidly growing trees, perhaps, in the world. This 
hybrid has clean-cut, glossy bright green leaves 
from two to three feet long with a sweet odor like 
that of apples, but it produces few nuts. Curiously 
enough the result of hybridization by using the 
pollen of nigra on pistils of calif ornica produces in 
abundance large nuts of a quality superior to that 
possessed by either parent. 

The famous Shasta daisy is the result of a mul- 
tiple crossing between an American and a Euro- 
pean species of field daisy and then between' these 
hybrids and a Japanese form. The fragrant calla^ 
known as 'Fragrance,' is decended from a single 
individual found by Burbank while critically ex- 
amining a block of Little Gem calla seedlings. 
He was surprised in this examination by a fragrance 
resembling that of violets or water-lillies ; as he 
had long been seeking a fragrant calla, the indivi- 
dual giving this perfume was carefully handed out. 



109 



Scientific Aspects of h.uther Burbank' s Work 




No farther selecting was done ; this plant was the 
single ancestor of the fragrant new race. 

And so one might go on for pages, but with 
slight variations in detail all these pages would tell 
only the same story: the stimulating or inducing 
of variability by environmental influences and by 
hybridizations ; the search after, and keen recogni- 
tion of, promising special variations; the selection 
of the plants showing these variations; rearing 
new generations from them, repeated selection, 
and new hybridizations to eliminate this character- 
istic or introduce that, and on until a desirable 
combination is found. Then the careful fixing of 
this form or type by repeated selection through 
several generations. 

But an end must be made of this. Let us, in 
a paragraph, simply sum up the essential things 
in the scientific aspects of Burbank's work. No 
new revelations to science of an overturning char- 
acter; but the revelation of the possibilities of 
accomplishment, based on general principles al- 
ready known, by an unusual man. No new 



110 



Vernon y m a n Kellogg 




laws of evolution, but new facts, new data, 
new canons for special cases. No new principle 
or process to substitute for selection, but a new 
proof of the possibilities of the effectiveness of 
the old principle. No new categories of varia- 
tions, but an illuminating demonstration of the 
possibilities of stimulating variability and of the 
reality of this general variability as the fundamen- 
tal transforming factor. No new evidence either 
to help the Darwinian factors to their death-bed, 
or to strengthen their lease on life ; for the 'man' 
factor in all the selecting phenomena in Burbank's 
gardens excludes all 'natural' factors. Here are 
some of Burbank's own words, touching these 
matters that scientific men are particularly inter- 
ested in, in his work : 

* 'All scientists have found that preconceived no- 
tions, dogmas, and all personal prejudice must be set 
aside, listening patiently, quietly and reverently to 
the lessons one by one which mother nature has to 
teach, shedding light on that which before was a 
mystery, so that all who will may see and know. 



Ill 



Scientific Aspects of Luther Bu? bank's Work 

* 'Crossing gives the raiser of new plants the 
only means of uniting the best qualities of each, 
but just as often the worst qualities of each are 
combined and transmitted, so that to be of any 
value it must be followed by rigid and persistent 
selection, and in crossing, as in budding and graft- 
ing, the afhnities can only be demonstrated by 
actual test. 

''All wild plants of any species are under almost 
identical environments, having their energies taxed 
to the utmost in the fierce struggle for existence. 
Any great variation under such circumstances is 
not likely to occur, and is much more likely to be 
stamped out at once by its struggling competitors, 
unless the variation should be of special use in 
competition, in which case it wdll survive, and 
all others may be supplanted by it. Thus we see 
how new species are often produced by nature, 
but this is not her only mode. Crosses and hybrids 
are very often found growing wild where two 
somewhat similar species grow contiguous, and if 
the combination happens to be a useful one, as it 



112 



Vernon h, y m a n Kellogg 




often does, the new creationjis encouraged by 
nature; then time and environment fix it, and 
man comes on the scene, perhaps ages later, and 
discovers it, and, not knowing all the facts, won- 
ders where the connecting links have gone. It is 
botanically classified as a new species, which it is 
most certainly. 

''In cultivated plants the life struggle is 
removed, and here we find variation almost the 
rule rather than the exception. 

''Varieties are the product of fixed laws, never 
of chance, and with a knowledge of these laws we 
can improve the products of nature, by employing 
nature's forces, in ameliorating old or producing 
new species and varieties better adapted to our 
necessities and tastes. Better food, more sunshine, 
less arduous competition, will of themselves induce 
variation in individual plants which will be more or 
less transmitted to their seedlings, which, selected 
consecutively through a certain number of gene- 
rations, will become permanent. Environment 
here exerts an influence as in all chemical cosmical 



113 



Scientific Aspects of Luther Burbank's Work 




and celestial movements. These small increments 
from environmental forces may produce a gradual 
or sudden change according to circumstances. 
The combustion of food liberates the moving 
force, environment guides it as it does the planets. 

'*When once the persistent type is broken up, 
old latent forces may be liberated and types buried 
in the dim past reappear. This, called atavism, 
is a concentration of ancestral forces — reverber- 
ating echoes — from varieties long since passed 
away, exhibiting themselves when from some 
cause, for instance crossing, present forces are in 
a state of antagonism, division, perturbation or 
weakness. These echoes, if collected by crossing 
and section, produce combinations of superlative 
importance and value.'' 

Finally, in any summation of the scientific 
aspects of Burbank's work must be mentioned the 
hosts of immensely valuable data regarding the 
inheritance of characteristics, the influence of 
epigenetic factors in development, the possibilities 
of plant variability, and what not else important 

114 



Vernon y m a n Kellogg 




to evolution students, mostly going unrecorded, 
except as they are added in mass to the already too 
heavy burden carried by the master of the labora- 
tory, and as they are summed up in those actual 
results which the world gratefully knows as Bur- 
bank's 'new creations.' 




115 



5 



I 



i 








4> 




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